Hey, to become an astronaut at NASA you would have to qualify some basic requirements as follows:

• At the very basic a bachelors degree in engineering, biological science, physical science or mathematics is required. You can even have a masters or a pH.D.
• A 20/20 vision either naturally or with corrective lenses.
• Blood pressure not more than 140/90 in a sitting position.
• A height between 62 - 75 inches(5.1 - 6.3 feet).
• And should have a good shape and maintained health.
• Lastly citizenship of the country in which you want to enroll into a astronaut program.

If u have all these qualities then you are eligible to become an astronaut. But apart from that you need to have pure determination and total hard work as getting a job as astronaut is not an easy task. No matter how many times you fail you gotta keep trying till you fulfill your destiny. I have provided a link below to gain more knowledge about the content. Hope this info was of help.
Best of luck for your career.

https://www.google.co.in/amp/s/amp.space.com/25786-how-to-become-an-astronaut.html